Ischemic heart diseases such as myocardial infarction still account for a high proportion of the death causes of the middle-aged and the elderly. Ischemic heart diseases are known to be induced by hyperlipemia which is a principal factor of atherosclerosis which is one of the adult diseases. Accordingly, the treatment of hyperlipemia which is a stage precedent to ischemic heart diseases such as myocardial infarction is essential, so that studies have been made for many years to develop an excellent hyperlipemia remedy.
Recently, an HMG-CoA reductase inhibitor has been developed as a hyperlipemia remedy and has been ascertained to have an excellent cholesterol level lowering activity. However, this inhibitor also hinders the biosynthesis of CoQ.sub.10 or dolichol, so that there is a danger of causing an adverse effect such as cardiac hypofunction, muscle ache or infirmity. Meanwhile, a desmosterol reductase inhibitor has a disadvantage that serious adverse effects such as cataract are caused by the accumulation of desmosterol.
Under these circumstances, it is still eagerly expected to develop a hyperlipemia remedy which is free from the above adverse effects and exhibits an excellent cholesterol level lowering activity.
Under the above circumstances, the inventors of the present invention started studies to find a compound having an inhibitory activity against squalene synthetase, and have found that a phosphorus-containing isoprenoid derivative can attain the object. The present invention has been accomplished on the basis of this finding.
Although some phosphorus-containing hydrocarbon compounds useful as drugs are disclosed in Japanese Patent Laid-Open Nos. 56492/1990 and 188288/1990, they are different from the compounds of the present invention in both structure and efficacy as drugs. Further, some phosphorus-containing isoprenoid derivatives useful as drugs are also disclosed in Japanese Patent Laid-Open Nos. 101088/1990 and 285821/1990. However, these derivatives are different from those of the present invention in structure.